When it came toPrince William and Kate Middleton's parenthood prep, not one stone was left unturned. The Duke and Duchess of Cambridge, due any day now with their first child, met privately with pregnancy guru Christine Hill for two sessions, a source confirms to Us Weekly.

In an interview with U.K.'sThe Telegraph newspaper, Hill, a 65-year-old mother of three who is a pediatric and obstetric physiotherapist and author of Christine Hill's Pregnancy Guide, told the paper that Middleton, 31, was a pleasure to work with.

"She's a delightful girl. What you see is what you get," she said.

Hill, who's retiring after a 35-year career, revealed that the expectant royal mother came to one session on her own and then the Prince, 31, joined her at their second session.

"[They're] a very strong team," she told the paper, adding, "Prince William will be doing the right stuff on the day."

As for what kind of tips she offers first-time fathers, including William, Hill explained, "I tell the fathers that the girl they hitched up with has gone for now – that she is fragile and vulnerable, and will be through pregnancy, labor and the first few weeks."

With Middleton due at any moment during London's scorching heat wave temperatures, Hill advises the first-time mom to relax. "Well, I'd say get your feet up, avoid swollen ankles, and thank God for flips!" she said.

While giving birth is no doubt a miracle and special time, Hill -- a no-nonsense expert -- told the paper she is realistic and honest with her clients about the experience.

"No one prepares you for the true ghastliness of birth," she said. "There's a sort of whimsical attitude that it will all be lovely and that everyone can have a natural birth. But that's not true."

And in Hill's opinion, all new moms, including Middleton, need downtime after giving birth. "[After birth, a woman should] “put a line through your calendar," she said. "Accept that this is going to change your life, that you will stay in a nightdress for a week.”